EDIT: 11/18/2018 - This is also working for OSX 10.13.x (High Sierra) and 10.14.1 (Mojave)

*************** I can not be responsible for any issues you may have so try this at your own risk******

Hi folks. I just wanted to chime in and fill you guys in on what I have found in my downtime with the 26x26 unit and the new Mac OS version.

Im glad to report that I have my trusty 26x26 running solid on both OS X El Capitan and Sierra.

Here is how I made it happen. Feel free to chime in with any you may have on this subject.

Now lets get down to business!

1: (Super important) Start with a clean install of OS X either 10.11.X (El Cap) or 10.12.X (Sierra) This means wiping your current system drive or testing with a spare drive you have lying around. Either way you are going to need to start the OS install from scratch.

2: Once you have OS X installed then go out and download/install all updates for the OS. lets get these updates installed and out of the way of making our trusty Firestudio 26x26 the king on this system. Update/reboot...repeat until all OS X updates are installed.

*****Please do not install any DAW software or hardware drivers yet********

3: Here is the technical part but it is very simple if you follow the instructions. We are going to disable "SIP" in OS X. This is the security feature that has been in OS X that keeps a lot of application and system files to not get install where they need to go.

Here we will disable SIP.Restart your Mac.Before OS X starts up, hold down Command-R and keep it held down until you see an Apple icon and a progress bar. Release. This boots you into Recovery.From the Utilities menu, select Terminal.At the prompt type exactly the following and then press Return: csrutil disableTerminal should display a message that SIP was disabled.From the  menu, select Restart.

***** Incase you want to re-enable SIP but you will not need to as it is the issue******(You can re-enable SIP by following the above steps, but using csrutil enable instead.)

Boom, that pesky SIP is now disabled and we can start to install our great 26x26.

Plug in the 26x26 unit to your mac via firewire. Power on the unit once it is plugged in.Now head over to the Legacy products of Presonus website and download the FireControl for Lion installer. (Fire Studio 26x26)

Run the Fire Control installer while the 26x26 in plugged in and powered on to the mac.Reboot the when the installer is complete. Do not try to access Fire Control surface before the reboot.

After the mac has booted back up and you have your trusty 26x26 plugged in to the mac and powered on and the sync light on the unit is solid blue you can now open Fire Control.

If Fire Control surface loads up and you can see the status and faders/ins/outs of the 26x26 unit you are in the house!

From here you can now install your DAW of choice and then plugins and so on.

dk39 wroteAnyone know if this works for High Sierra too? Very encouraging news, thanks @tomorrowstk and @Sammy D

Hi just upgraded my MacBook Pro from Yosemite to High Sierra and on first look it works with my Firestudio 2626 using these instructions. I did not do a fresh install, but the MacOS upgrade. I did however, have to re-install FireControl. I couldn't find this file on the PreSonus website anymore, but fortunately saved the .dmg when I downloaded it a few years ago.

Only tried 2 channels of output, but thus far worked OK! Will check input and more channels further, and test with the MSR later.

I really like this interface, and it would be too bad to have to get rid of it. So far, I'm pleased that it may be able to continue to work!